The invention relates to a method for automatically setting the voltage resolution in particle beam measuring devices.
In electron beam measuring devices, the voltage resolution .DELTA.V.sub.min in the measurement of signal curves is a function of the band width .DELTA.f of the measured signal processing and of the current I.sub.PE of the primary electrons incident upon a measuring location ##EQU1## where c is a proportionality constant. The measurement of a signal curve at a measuring location with a specific voltage resolution requires a balancing or matching of the two parameters, namely, the band width .DELTA.f and the beam current I.sub.PE. In practice, the beam current I.sub.PE is thus held constant.
Up to now, there were two possibilities for setting the voltage resolution according to the prior art. Given both possibilities according to the prior art, the beam current I.sub.PE is held constant. According to the first of these two possibilities known from the prior art, the desired voltage resolution is prescribed and the required band width .DELTA.f is then calculated according to the above-specified equation. This known method has the disadvantage that the proportionality constant c is material-dependent and topography-dependent. Moreover, it is also required for such a calculation that the beam current I.sub.PE be known, this depending, among other things, on the selected width and on the frequency of the primary electron pulses in an electron beam measuring device. This method for calculating the required band width .DELTA.f is therefore complicated and imprecise in practice.
Given a second method known from the prior art for setting a desired voltage resolution, this voltage resolution is subjectively set by an operator by manual selection of the band width .DELTA.f. Such a method is not always successful, so that it is often necessary to repeat signal curve measurements with a modified band width.